Câu 12
\(K\left(a;b\right)=>\overrightarrow{AK}=\left(a-2;b-5\right)\)
\(\overrightarrow{CK}=\left(a-5;b=1\right)\)
\(\overrightarrow{BC}=\left(4;-4\right)\)
\(\overrightarrow{AK}=3\overrightarrow{BC}+2\overrightarrow{CK}< =>\left[{}\begin{matrix}a-2=3.4=2\left(a-5\right)\\b-5=3.\left(-4\right)+2\left(b+1\right)\end{matrix}\right.\)
\(< =>\left[{}\begin{matrix}a-2=12+2a-10\\b-5=-12+2b+2\end{matrix}\right.< =>\left[{}\begin{matrix}a=-4\\b=5\end{matrix}\right.\)
\(=>K\left(-4;5\right)\) => Chọn A
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